linux-kernel - Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732

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Message-ID: <CAJZ5v0ig1qTTMw5GHO_-vuyETD46tin8bS2deyvtw0OvuDSCng@mail.gmail.com>
Date:	Sat, 9 Apr 2016 14:33:38 +0200
From:	"Rafael J. Wysocki" <rafael@...nel.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Peter Zijlstra <peterz@...radead.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	Doug Smythies <dsmythies@...us.net>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732

On Sat, Apr 9, 2016 at 8:40 AM, Mike Galbraith <umgwanakikbuti@...il.com> wrote:
> On Fri, 2016-04-08 at 22:59 +0200, Rafael J. Wysocki wrote:
>> On Friday, April 08, 2016 08:50:54 AM Mike Galbraith wrote:
>> > On Fri, 2016-04-08 at 08:45 +0200, Peter Zijlstra wrote:
>> >
>> > > Cute, I thought you used governor=performance for your runs?
>> >
>> > I do, and those numbers are with it thus set.
>>
>> Well, this is a trade-off.
>>
>> 4.5 introduced a power regression here so this one goes back to the previous
>> state of things.
>
> That sounds somewhat reasonable.  Too bad I don't have a super duper
> watt meter handy.. seeing that you really really are saving me money
> would perhaps make me less fond of those prettier numbers.

You can look at the turbostat Watts numbers ("turbostat --debug" and
the last three columns of the output in turbostat as included in the
kernel source).

That requires an Intel CPU with RAPL.